Organometallic complexes, particularly complexes of rhodium, are well known to catalyze a variety of useful organic reactions, including for instance, hydrogenation, oxidation and carbonylation of olefinic reactants in connection with the synthesis of pharmaceuticals, dyes, insecticides, solvents, detergents, and other valuable products.
In conventional practice, catalytically active rhodium complexes have principally been applied in homogeneous form, in solution in an organic reactant phase. As such, their use has suffered from the difficulties inherent in the recovery of homogeneous catalysts from the reaction products. Effective catalyst recovery has often been a necessity when applying such complexes, because of the value of the complexes and/or because of the requirements for product purity.
As described in U.S. Pat. No. 4,248,802, it is also known that aqueous solutions of rhodium complexes can be applied to catalyze conversions of water-immiscible reactants. However, such immiscible aqueous catalyst solutions have generally exhibited low activity, possibly attributable to the low interfacial area between aqueous and organic phases.
Several catalysts have been reported which support an organometallic complex on a solid surface in the form of a liquid solution in a (nonaqueous) solvent. In conventional practice, such catalyst systems have been applied to promote vapor phase reactions. Condensation of reaction products from the vapor phase onto the surface of the liquid catalyst phase has proven to be troublesome. In cases in which the catalyst support material is a porous solid, product condensation can result in blockage of the pore void spaces. Attempts to solve the problems caused by condensation have generally centered upon increasing the temperatures at which the catalyst is applied, although this in turn has led to loss of catalyst components (e.g., solvents and ligands) through evaporation from the supported liquid phase and to degradation and deactivation of the organometallic complex.
The principal object of this invention is a heterogeneous catalyst system suitable for application in liquid reaction mixtures, which comprises an organometallic complex of rhodium immobilized in a catalytically-active, essentially non-leaching form on a solid surface.